Second to fourth digit ratio: a predictor of prostate-specific antigen level and the presence of prostate cancer


Tae Beom Kim, Department of Urology, Gachon University Gil Hospital, 1198 Guwol-Dong, Namdong-Gu, Incheon 405-760, Korea. e-mail:


Study Type – Diagnostic (exploratory cohort) Level of Evidence 2b

What’s known on the subject? and What does the study add?

The Homeobox genes, Hox a and d, control urinogenital system differentiation and digit development. The patterns of digit formation may be related to gonad function and may be reflected in 2nd to 4th digit ratio (digit ratio). Digit ratio is negatively correlated with prenatal testosterone levels and androgen receptor activity which is related to the increased prostate cancer risk.

Patients with a lower digit ratio have a higher risk of prostate biopsy due to high PSA level, and of prostate cancer. Digit ratio could be a predictor of high PSA level and the presence of prostate cancer.


To investigate the relationships between the 2nd to 4th digit ratio (digit ratio) and prostate volume, prostate-specific antigen (PSA) level, and the presence of prostate cancer.


Of the men that presented with lower urinary tract symptoms (LUTS) at a single tertiary academic center, 366 men aged 40 or older with a PSA level ≤40 ng/mL were prospectively enrolled. Right-hand 2nd and 4th digit lengths were measured prior to the PSA determinations and transrectal ultrasonography (TRUS). Prostate volumes were measured by TRUS without information about digit length. Patients with a PSA level ≥3 ng/mL underwent prostate biopsy.


No relationship was found between prostate volume and digit ratio [correlation coefficient (r) =−0.038, P= 0.466]. But, significant negative correlations were found between digit ratio and PSA (r=−0.140, P= 0.007). When the patients were divided into two groups (Group A: digit ratio <0.95, n= 184; Group B: digit ratio ≥0.95, n= 182), Group A had a higher mean PSA level than Group B (3.26 ± 5.54 ng/mL vs 1.89 ± 2.24 ng/mL, P= 0.002) and had significantly higher risks of prostate biopsy [odds ratio (OR) = 1.75, 95% CI = 1.07–2.84] and prostate cancer (OR = 3.22, 95% CI = 1.33–7.78).


Patients with a lower digit ratio have higher risks of prostate biopsy and prostate cancer.